Antenna for producing elliptically polarized waves



Tl'. oo ONE 4 8. TL.y U 1 mm `N 5: WR ,M l l anw, IJQf/H 2% n N.. W E m 2 H E Y m m B Mw E Y@ Tum EA. L nlv mm1 Run D. ...mA Hmm Il om.. w O Dn P o H 2 D0 /I F A N m l. m G i A .lli rr April 14, 1953 Patented Apr. 14, 1953 .ANTENNA ol'fVA PRODUCING "ELLIPTICALLY POLARIZED I Hem-y1 vJ. -Rib1et,. Cambridge,l Mass., assignony by rmesne assignments, to the United States of America. as, represented by the. Secretamof `War Application Apii 3, 1945', Serial' No. 5865416 invention Hrelates -`to `-antennas for radio object-locatingv systems. I The invention'is particularly-directed to an antenna embodying lafwave .guide transmission line designed to producey cirycularly polarized electromagneticradiation: that vis.:radiation such thatv at a given pointtheielectric' vector isof' constantrmagnitude and rotates at' uniformV speed. The; invention relatesv equally to` the vcoaxial conductor yand holloweppe" type wave guidegtransmission lines.

antenna having the characteristics `for producingr a circularly polarized radiation hasymany useful applications. VFor example,v itmay be'used as a beacon `antenna capable of'operatinginV conmotion with either vertically orrhorizontallypolarized radio object-locating. Systems.

' 'The principal object ofthe present invention is; toprovidea simpleA and inexpensive; radiating array type.. antenna.. comprising a, waveguide or coaxial line, which, whendisposed in its contemplatedyertical. position, ispadapted toradiatecircnlarly polarized electromagnetic waves ci energy.

VAnother object` of. the4 invention. to provide a.. slotted Wave` guide. antenna system which. is substantially `non.-directional in the.. horizontal planeA but which is relatively sharply directional (to a controllableextent, if desired) inthevertical plane, and, moreoveiyin which Vthe waves are circularly polarized (polarization being de- :Inedin'v the sense used'inthe radio art' rather thanv in theopticar sense. and referringl hereto the direction ofthe electric vector rather' than thai/'ofthe magnetic vector).

' Otherlobjects and novel featuresV ofthe inventionjwill become apparent as vthefpresent 'description proceeds.

'.Inthe. drawings:

Fig. ll is a partialv front elevation view of a waveguide antennaernbodying the present invention;

"Fig, 2' isal partly broken-awayperspective of thesamerand' Fig. 3""is a vertical;sectionalviempartly bro.-

kengaway, of a 'modicationjofv` the. antenna^` shown in Flai'.

In.' generali the invention comprises al length,

\ of. high4 Afrequency conductor.. suoli as. a coaxial line `or wave ,guide adapted `for interchange.. of` radiantenergy with surrounding `space through a .system of. longitudinally disposed `slots and a seriesof ooncentricrines .of .,conducting.materiali Slacedasmall; distance..v apart. and. separated by. dielectric. materiali such. as.. polystyrene., or the` lketo; iorm ..circun1ierential1y disposedjslots.; The

longitudinany and circumferentiany disposed@ (Cl. Z50-335,3):

`2l slots are suitablzsg` positie ed relativeftoeaclr other to; produce.y circul'arly; polarized radiation. as more `clearly disclosed hereinafter.

The waveguide I .shownV in the drawings: is of. the. cylindrical typaa-ndit: is adaptedby'reason lof its dimensions,. iin-accordance withwellknown principles, 1 to.` transmitxelectric Ywaves in.` the Eo or "1`Mo,1mode.- of: transmission. When.l operating-A in thismode, the; walliof: the wave guide I'll normally havefr longitudinal oscillating: currents, but: no. transverse:` oscillating: currents', 1 as contrasted` .withl the. Ho. or TEM: mode. in. a'frectarrendarl wayea guide, wherez both. longitudinal and transverse4 currents;` are found;

waveguide II)` is formed-uffa. plurality .ot aligned hollow-u and cylindrical sections IrI `ci? metal or:l other electrically `conductive material. Eachof: sections'. I-IV isnaxially spaced from4 its next adjacent: sectionaa small distanceL compared' to the `length of eachsection which may. be determined in. accordance with. impedance matching requirements and for purposes: dened hereinafter;

' Diskylikefmembersor rings I2 of dielectric materialaren mounted coaxially 'with' sections Ill'. Any `usualffsolid= dielectric material, such as polystyrene; mayA be` usedfor members I2; the f coeiiicientiofexpansion ofthedielectric being preferably: comparable to that of the Ametallic sections II for mechanical reasons. The-circumferential portionv of each diska-likevmember" orring I2"I is located between the-end`s of'acljacent4 sections H and servesrto---space sections I-'I*. If desired,v members I 2=when the shapei-ofaring maybe of substantially the same radial dimensions as the lthickness of themwall of" sections II or as disk shaped members lmay completely or only `par-tiallyiill the-insidefofV Wave guide I llA as indi"- cated in Figs; 3I and 2, respectively. When it is desiredi that' members `I2 serve,` to lill`- the4 inside ofA wave guide-I I0 it is preferred thateach .member.w lbefin'thefform-of a s-olid cylinder having aflength:` offone wavelength, each member I2 abutting its adj acent member atl a. point alongf t-hez lengthof each -section II; If desired; the circumferenti'all portion .of`` members `or rings' Il2" may be= provided f'withannular anges I 4 (Fig: 3)j having atsutableaxialldimension to lit' betweenh adjacent sections IIandserveto space thesame. Circumferentialsurfaces of" rings or members 'I 2" or off' iiangesv` I4 between adjacent sections are preferablymade'iiush with the outer surface of;` guide I I) so that "the `outer wall of' gudevl'v pre` sents a smooth; cylindrical surface. `The distance, between"-corresponding points on an adjacent`sec` tion II is approximately equal to the wavelength of the energy inside the conductor or guide I0. Also, the distance between corresponding points on adjacent portions of flanges I4 is equal to a Wavelength. Radiation of energy occurs from the several circumferential regions or slots, formed'between conductor sections II bythe dielectric member or ring I2, in directions normal tothe axis of guide ID. Because of the abovementioned spacing such radiation will be in phase as is well known in the art. With the antenna.

position, the wave energy radiated from the circumferential slots will normally have a vertically polarized characteristic.

Each of sections II is provided withV a'seriesV of substantially equally spacedvparallel slOts I5 adapted to radiate waves of energy from wave .the wavelength in the guide, will be circularly vpolarized due to the fact that space quadrature guide Ill. In order to obtain the desired circularly polarized radiation of radiated energy Waves, it is necessary that slots I5 beso positioned that the waves radiated by slots I5 will be in the proper phase relation with the energy waves emitted through circumferential dielectric portions I3. The slots I5 are consequently longitudinally oriented in each of sections II so that each slot is parallel to the axis of the wave guide I0 and perpendicular to the planes of the dielectric members or rings I2.. Slots I5 are of equal dimensions and are arranged so thateach slot I5 is equally distant from both ends of its corresponding section II, thereby forming a ring of spaced parallel slots about the circumference of each section II. Thespacing between successive rings of slots measured longitudinally of the wave guide I0 between centralplanes is designed to provide the desired phase difference. Accordingly, such spacing should be equal to the wavelength of oscillations in the wave guide l0.

In order that the radiation maypass through thev slots in .appreciableA amounts, the electric field of the waves in the waveguide is distorted in the neighborhood of the centers of the slots by means of radially Y disposed projections or probes of metal or other electricallyA conductive material such as the screws I6. extending radi,- ally into the wave guide I0, as shown `in Fig. 3.

The ldirection and intensity of the transverse electric field across the slot is determined by the length of screwsV I 6.

For longitudinal spacings between centers of the order of one wavelength the screws of successive slot rings will be similarly placed (nonreversed array) instead of oppositely placed (reversed array).

The phase of radiation from the circumferential slots (the circumferential space between adjacent sections II lled by the dielectric member or ring I2) is that of the current across these circumferential slots. The phase of radiation from the center points of the longitudinal slots I5 such as at A is that of the resultantvoltage vector at such points A. Since the phase angles of the voltage and current vectors' depend on the propagation constant of the conductor line and on the reflection factor, the desired 90 time phase diierence, between voltage vector and current vector at the circumferential and longi-V tudinal slots respectivelymay be obtained by proper adjustmentsA of the depthA of projection of the screw probes II6 into the`wave guide I0 and byv providing an adjustable terminating plunger' I'I -(lig. l) at'one' end' of the line asv is Well known in the art. `The effect of all the circumferential slotswill be additive since theyy this is the wave guide I0, disposed in" a 'vertical 'alsoexists The magnitude of the voltage vectors maybe made equal by proper adjustment of the depth of screws .I6 and the Width or axial dimension of the circumferential slots or regions between the adjacent ends of sections II.

From the foregoing description it will be clear that fundamentally there has been disclosed an antenna structure for radiating circularly polarized waves or more generally elliptically polarized f waves comprising `a metallic waveguide having means for radiating or receivingfradio frequency energy which is comprised of at least one slot shaped aperture in the wall of the guide which is oriented for a maximum radiation of energy from the guideand at least one slot shaped aperture in the wall of theguide which is oriented perpendicular to the rst aperture normally to radiate a minimum'of energy from the guide and means extending and adjustable into the guide are provided for coupling energy therefrom to the second aperture. in order to provide radiation therefrom having a time phase displacement relative to the radiation from .the first aperture'of ninety electrical degrees.

While the present description has been principally directed to a wave guide of circular crosse' section, it will be understood that the invention is not limited. to this structure. For example. by suitably arranging the longitudinal and circumferential slots, circularly polarized'radiation may be produced with wave guide or coaxial conductor of elliptical or rectangular cross-section. It will alsov be understood various other modifications and improvements may be made Within the scope of the present invention'and therefore it is not desired that the invention be limited to the precise details set forth herein.

What is claimed ist ,1. An. antenna array comprising a transmission line havingr a' tubular' wave-guiding 'wall' withinv which high frequency electromagnetic waves are propagated. said wallcomprising a plurality of axially aligned individual metallic sections. said sectionsV being spaced a predetermined distance Y thereby forming circumferentially disposed slots length of the guidedwave. each of saidmetallic.

sections having a plurality of parallel longitudinal slots arranged with the long dimension of eachjslot parallel to the axis of said line, said slots being substantiallyequally spacedabo'ut the circumference of each section so that the ends of each ofsaid longitudinal slots are equi-I distant from the adjacent ends of each section.`v

and at least' one'rn'etallic projection associated' with each of said longitudinalslots mounted on' saidl waii-nearthe midqmbf said lcnsitudnia'ljl demand-.extending mi@ `said transmita@ 11nesaid projection beingzeieetive to cause radiation through "said longitudinal slots in'suitable amplitudad phase relationshipwith the radiation through said circumferential` slots to produce circularly` polarized radiationiin a beam which jis"`sub"stantially non-directional in a horizontal plane and which is relatively sharply directional a vertical plane. i,

plurality of aligned individual conductive sections, said sections being spaced a predetermined distance, the spacing between adjacent sections forming circumferential slots in said wall, a plurality of dielectric cylindrical members, each of said members being disposed coaxially within said sections, the circumferential portion of each member disposed in said circumferential slots being substantially flush with the outside surface of said sections, the axial distance between corresponding points on adjacent sections and on yadjacent dielectric members being substantially equ-al to a wavelength of the guided wave, each conductive section having a series of slots circumferentially spaced around the section and longitudinally oriented with the long dimension of the lslots parallel to the axis of the guide and with the ends of each longitudinal slot being equidista-nt from the adjacent ends of each section, `and at least one metallic adjustable projection mounted on said wall near the middle of each Vlongitudinal slot and extending into said wave guide, said projection being adapted to distort longitudinal currents in said tubular wall when said wave guide is excited and thereby to provide for flow of wave energy through said longitudinal slots, said projections being so disposed with respect to said longitudinal and circumferential slots to provide 90 time phase difference between the energy at the circumferential and longitudinal slots whereby circularly polarized radiation from said slots is produced.

3. An antenna array including a hollow cylindrical wave guide within which high frequency electromagnetic waves are propagated, said wave Vguide comprising a plurality of spaced aligned conductive sections, the space between said sections aiording circumferential slots around the guide adapted to radiate energy to surrounding space, a dielectric member disposed in each of said circumferential slots, each of said conductive y.sections having a plurality of longitudinal slots therein oriented with the long dimension of the slots parallel to the cylindrical axis, each of sa1d longitudinal slots being equidistant from the adjacent end of each section, at least one metallic projection mounted on said wave guide near the midpoint of each longitudinal slot and extending into said wave guide, said projections being effective to cause radiation from said longitudinal slots, the axial distance between corresponding points on adjacent sections being substantially equal to a wavelength of the guided waves whereby a 90 time phase relationship and space quadrature exists between radiations from said longitudinal and circumferential slots whereby the resultant voltage vector rotates to produce circularly polarized radiation.

4. An antenna array including a hollow cylin- .Y l avertie aan ne Y j, fA electromagnetic' energy; areV propagated.

4saia',iii-wegindscomprising@ pier ity or spaced 'alignedlindividual lsections of ele tically'cond uctive 'niaterial,` the spaces between said Sections affording slotjshaped circumferential regibns around thek guide] f0r"`nesy te L radiate .th -tiiroiig'ii eaiicfjsaid sectiorisgiiayis radi 'Slbshi tions 1being a wavelength of the'fnergyinisaid wave guida' and'` means adjustably extendable into said guide adjacent each one of said radiating means to provide a 90 time phase relationship between radiations from said circumferential regions and said radiating means to effect circularly polarized radiation from said wave guide.

5. An antenna array including a tubular transmission line for propagation of high frequency waves of electromagnetic energy, said tubular line being provided with two series of slots therein, the longitudinal axes of the slots of one of said series lying in planes perpendicular to the axis of said tubular line, the longitudinal axis of the slots of the other of said series lying in planes parallel to the axis of said tubular line, and a metallic projection into said tubular line adjacent each of said slots of said other series for producing radiation therefrom with a phase shift of 90 with respect to the radiation from the slots of said one series, the centers of the slots of one of said series being axially spaced a half wavelength of the energy in said line from the centers of the slots of the other of said series to produce elliptically polarized radiation from said line.

6. An antenna structure for radiating elliptically polarized waves comprising a metallic wave guide having means for radiating energy applied thereto, said guide comprising at least one slot-shaped aperture oriented with the long dimension perpendicular to the longitudinal axis of said guide and approximately symmetrically disposed about 'a current maximum point, at least one slot-shaped aperture oriented with the long dimension parallel to the longitudinal axis of said guide and approximately symmetrically disposed about a current minimum point, the respective centers of said first-mentioned and said secondmentioned apertures being spaced along the length of said guide approximately a distance of one-half wavelength at the operating frequency of said energy, and adjustable means extending into said guide adjacent to said second-mentioned aperture for coupling energy from said guide to said second-mentioned aperture and for varying the propagation constant of said guide, whereby the propagation constant of said guide may be adjusted to a value which makes the distance between said centers of said apertures exactly one-half wavelength at the operating frequency of said energy.

'7. An antenna structure for radiating elliptically polarized waves comprising a metallic wave guide having means for radiating energy applied thereto, said guide comprising at least one slot-shaped aperture oriented with the long dimension perpendicular to the longitudinal axis of said guide, at least one slot-shaped aperture oriented with the long dimension parallel to the longitudinal axis of said guide, the respective centers of said first-mentioned and said secondymentioned apertures being spaced along .the

length of said guide approximately a distance of one-half wavelength at the operating frequency .varying the propagation constant of said guide,

whereby the propagation `constant of said guide may be adjusted to a value which makes the distance between said centers of said apertures ex- V,actly one-half wavelength at the operating frequency of said energy.

' HENRY J. RIBLET.

References 'cited 1n the me' or this patent"- UNITED STATES PATENTS Number Name Date Runge Dec. 27, 1932 Hammond, Jr June 27, 1933 Southworth July 9, 1940 Dallenbach May 6, 1941 Fiske Sept. 3, 1946 

